Method for the production of magnetic strips or tapes



H SPRUNG METHOD FOR THE PRODUCTION OF MAGNETIC STRIPS OR TAPES Nov. 6,1934.

Filed Aug. 11, 1953 /N [/5 N TOR H. SPRUNG A TTORNE V Patented Nov. 6,1934i- METHOD FOR THE PRODUCTION OF MAGNETIC STRIPS OR TAPES 4 HelmutSprung, Berlin oberschoneweide, Germany, assignor to General ElectricCompany, Schenectady, N. Y., a corporation of New York ApplicationAugust 11, 1933, Serial No. 684,771

In Germany August 16, 1932 6 Claims. (Cl. 175-21) It has previously beenproposed to produce sheet metal, wire, and strip cores and Krarupwindings which are made of a ferromagnetic material which after anydesired saturation with direct current field, has an instability of lessthan with an initialpermeability of w= andmore. In the production ofstrip cores it has been found that when the strip is simply wound up,the elastic stresses set up in it, lead to an appreciable deteriorationof the magnetic properties, particularly the hysteresis. On this accountit has been proposed in the case of strip cores to obtain the requisitebending by plastic deformation either by bending the strip at regularintervals or by first winding the strip on a very much thinner mandreland subsequently allowing it to expand to the desired diameter. Thefirst process is accompanied by the disadvantage that the core no longerpossesses a circular shape and can therefore only be wound with anuneconomical'utilization of the available space; the second processpossesses the disadvantage that the core after expanding can no longerbe wound so tightly.

The object of the invention is to provide a process for the productionof strip-cores in which these disadvantages are eliminated byplastically deforming the strip of ferromagnetic material a number oftimes in different directions before it is wound into a core so that itloses its springiness to an appreciable extent and it is then given afinal change of shape such that it does not exhibit any further elastictension after being wound up. For this purpose the plastic deformationand winding may advantageously be carried out in one working process.The repeated plastic deformation may be done in various ways. Oneprocess which has been found particularly suitable is that in which thestrip is drawn between two rows of rollers which are set with repect toone another in such a way that the rollers in one row stand opposite thegaps in the other row and engage in these gaps. The diameter of therollers in one row is preferably selected somewhat greater than thediameter of the rollers in the other row.

A diagram of one apparatus suitable for the production of strip coresaccording to the invention is illustrated in the drawing by way ofexample.

In the drawing the strip 1 is wound into a core 3 on the mandrel 2. Themandrel may be driven in any desired manner, for example, by means ofgear wheels 4 and 5. Before being wound up, the strip is plasticallydeformed a number of times in oppositedirections according to theinvention by drawing it between the rollers 6 and '7 which may consistof steel, for example. The

rollers are arranged in such a way that the rollers 'Z, the diameters.of which are the smaller, are always opposite the gaps in the rollers6. The distance apart of the two rows of rollers may be altered by meansof the pressure screw 8, according to the nature and composition of thematerial employed. The smaller the distance between the two rows ofrollers is, or the more the rollers having the smaller diameter projectinto the gaps between the rollers having the larger diameter, thegreater will be the plastic deformation. On leaving the rollers thestrip will have a permanent bend on the side of the smaller rollers.This bend must be of such size that the strip on being wound up willpossess little or no elastic tension. The size of the bend will dependupon the diameter. of the rollers and their mutual position with respectto one another and also upon the tensile stress during the drawingoperation, as the bend may be partially neutralized by the tensilestress. In accordance with the diameter of the core to be wound,therefore, the separate factors must be adjusted in such a way that thebend has the requisite size. Furthermore, precautions must, of course,be taken that the strip receives its permanent bend in the direction inwhich it is subsequently to be bent as a core.

The above described method of production possesses the further advantagethat any rough edge or ridge formed by cutting the strips is pressedflat by the rollers so that a special flattening process is renderedunnecessary.

The insulation of the strip. core is carried out in a known manner.Since the core will have no further spring expansion after being wound.it is possible to allow athin paper strip to run in with it, very littledanger existing of the paper strip tearing, which was often the case inthe hitherto customary process. Moreover, insulation may also be appliedby impregnating the strip before or after winding in any liquid oreasily readily flowing insulating medium, such as lacquer or likeinsulating mediums. and further in isinglass or similar materials andgenerally in' all insulating mediums which are employed for solid cores.

i What is claimed is:

up, so that it loses its spring power to an appre- 4. Process accordingto claim 1, characterized by that for purposes of insulation a thinpaper strip is wound up parallel with the strip itself.

5 Process according to claim 1, characterized in that the strip isimpregnated in a liquid or readily flowing insulating medium before orafter winding.

6. Process according to claim 1, characterized in that the strip isinsulated by chemical treatment of the surface.

HELMUT SPRUNG.

